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May 18th, 2009, 12:54 AM   #1
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...the plumber charges

A plumber charges $93 for a job which takes 2 hours and $141 for 4 hours of work. Let $C be the plumbing cost for t hours of work. What is the linear rule connecting C and t?
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May 18th, 2009, 02:01 AM   #2
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Re: ...the plumber charges

How far have you got with this problem? Do you understand what a linear relation is?
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May 18th, 2009, 04:47 AM   #3
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Re: ...the plumber charges

Don't let the variable names fool you. You re being asked to extend your thinking beyond "x" and "y" to apply it [gently at first] to "real world applications". Think of two point on a lone with "C" being your "y" and "t" being your "x". If still in doubt, replace C and t by x and y and try that, then repeat with the given variables.

["Real world"? Where do you find a plumber who charges only $93 for any job??]
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May 18th, 2009, 05:10 AM   #4
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Quote:
Originally Posted by Voltman
A plumber charges $93 for a job which takes 2 hours and $141 for 4 hours of work. Let $C be the plumbing cost for t hours of work. What is the linear rule connecting C and t?
You are given two data points: (t, C) = (2, 93) and (t, C) = (4, 141).

Plug these into the formula for "slope" to find the slope of the rule.

Then pick either one of the points (it doesn't matter which), and plug it and the slope you just found into one of the formulas for the equation of a straight line.

Solve the result for "C=" to find the rule.
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